Automatic transmissions are commonly used automotive applications as a driver convenience feature. In many transmissions, a single shift schedule map is used to determine points when the transmission is shifted from one gear to another. The shift schedule is predetermined and may be optimized for fuel economy and performance for a certain vehicle load and with acceptable drivability. The shift points are a typically a function of throttle position and vehicle speed, and do not take into consideration the load on the vehicle. It is known to provide a towing or hauling switch, which may invoke an alternate shift schedule. Again, this towing schedule is pre-programmed and hence is not a function of the actual load on the vehicle, nor is it able to be dynamically updated based on other changes in operating conditions.
During operation of an automatic transmission, a cycle can occur during which the transmission upshifts automatically, vehicle speed slows, and then the transmission downshifts automatically. The reduction in speed may result from increased loads or a decrease in powertrain available power. This is cycle is sometimes referred to as powertrain hunting. The rapid succession of gear shifts may be unexpected, and can detract driver satisfaction.